Abstract: The invention relates to spiropyran compounds. They have the general formula (I): ##STR1## in which: X represents the CH.sub.2 group or a sulfur atom; R.sub.1 and R.sub.2 represent electron donor and/or acceptor groups selected for instance from the group NO.sub.2, COC.sub.6 H.sub.5, CN, the halogens, the acyl substituents, alkoxy substituents, the hydrogen atom, the alkyl and mercaptoalkyl groups, the ethers of the formula CH.sub.2 OR, thioethers of the formula CH.sub.2 SR and amines of the formula CH.sub.2 NR.sub.2 in which R represents an alkyl group; R.sub.3 is a linear or branched alkyl group, having 1 to 18 carbon atoms, or an arylalkyl or alkenyl group.--R.sub.4,R.sub.5,R.sub.6,R.sub.7,R.sub.8 and R.sub.9 have one of the meanings indicated for R.sub.3 or represent, two by two, with the group in ortho position, a --(CH.sub.2).sub.n -- group in which n is a number between 5 and 10.R.sub.10 represents a hydrogen atom if X=S and if X=CH.sub.